Conventionally, a fluid processing apparatus for seawater desalination, etc. has been constructed such that as shown in FIG. 7, a plurality of unitary modules 10 each comprising a cylindrical vessel 1 incorporating therein a plurality of separating elements 2 each comprised of a piece of reverse osmosis membrane (permeable membrane). The separating element 2 is formed by spirally winding a piece of permeable membrane around a central pipe 11 through a spacer. Thus, when seawater is supplied under pressure from a supply pipe 12 into the unitary module 10, the seawater is desalted through the separating element 2 in each stage and the low-pressure fresh water after desalination is discharged from a discharge pipe 13 through the central pipe 11 while high-pressure concentrated water is discharged from a discharge pipe 14.
That is, the cylindrical vessel is divided into a high-pressure space where high-pressure seawater and concentrated water are present and a low-pressure space where the low-pressure fresh water is present, through the permeable membrane of each of the separating elements 2.
However, the conventional fluid processing apparatus has generally been constructed such that as shown in FIG. 8, a plurality of unitary modules 10 are fixedly arranged horizontally on frames 20 and supply pipes 12 and discharge pipes 13, 14 which respectively extend from both side ends of the unitary modules 10 are collected into a manifold 22 and manifolds 23, 24.
However, there has arisen the problem that since the installation of the frames 20 and the piping operation for connecting the manifolds 22, 23 and 24 at the working site are extremely complicated, the cost required for these operations becomes higher than the cost of the apparatus itself. Further, there has also arisen the problem that if the manifolds 22, 23 and 24 are attached to both ends of the unitary modules 10, the manifolds are required to be dismantled or assembled every time when each of the separating elements 2 is periodically exchanged resulting in making the maintenance operation extremely inefficient.
Moreover, where separated fluid is produced by the above-described processing apparatus, it has been usual that since high-pressure seawater or concentrated water flows through the manifolds 22 and 24, the pressure loss of these manifolds becomes significant causing the load of the related pump or the like to be quite heavy. Consequently, the availability factor of the apparatus as a whole is low and as a result, the method of producing the separated fluid by using such apparatus has been inefficient.